Synthetic smectite compositions, their preparation, and their use as thickeners in aqueous systems

ABSTRACT

A process for preparing novel synthetic smectite compositions related to saponite plus accessory hydrous magnesia, and the resulting products. The novel substances have extraordinary swelling and gelling properties in aqueous solutions, including strong electrolyte solutions, and have other specific utilities depending therefrom. The synthetic smectite compositions have the following formula per unit cell: ((Mg6AlxSi8 x O20 (OH4 aFa) x XMZ/z ) +yMg (O,OH) in which the contents of the braces constitutes the unit cell, M is an alkali metal cation, an alkaline earth metal cation, an ammonium ion, or mixtures of such ions, y Mg (O,OH) is the variable amount of accessory phase occluded therewith, and x, y, a, and z have values within the following ranges: 0.1 &lt; OR = X &lt; OR = 1.5 0.1 &lt; OR = Y &lt; OR = 2 0 &lt; OR = A &lt; OR = 2 1 &lt; OR = Z &lt; OR = 2.

llited States atet [191 Granquist [4 1 Dec. 17, 1974 SYNTHETIC SMECTITECOMPOSITIONS,

THEIR PREPARATlON, AND THEIR USE AS THICKENERS IN AQUEOUS SYSTEMS [75]Inventor: William T. Granquist, Houston,

[21] Appl. No.: 257,303

[52] US. Cl 252/317, 106/20, 106/286, 106/287 S, 106/288 B, 117/362,252/8.5 A,

OTHER PUBLlCATlONS Bragg et al.: Crystal Structures of Minerals, London1965, pages 346349; 352-353. Meier: page 17 of article entitled ZeoliteStructures," in Molecular Sieves, Papers of Conference in London on Apr.46, 1967; Society of Chemical Industry, London, 1968.

Deer et al.: Rock Forming Minerals, Vol. 3, Sheet Silicates, London1962, pages 170-171; 226-227.

Primary Examiner-Richard D. Lovering Attorney, Agent, or Firm-Delmar H.Larsen; Roy F. House; Fred Floersheimer [57] ABSTRACT A process forpreparing novel synthetic smectite compositions related to saponite plusaccessory hydrous magnesia, and the resulting products. The novelsubstances have extraordinary swelling and gelling properties in aqueoussolutions, including strong electrolyte solutions, and have otherspecific utilities depending therefrom. The synthetic smectitecompositions have the following formula per unit cell:

g6 J 8-I O20 4 u u I XMZ/Z (0,0H) in which the contents of the bracesconstitutes the unit cell, M is an alkali metal cation,-an alkalineearth metal cation, an ammonium ion, or mixturesof such ions, y Mg(0,0H)-is the variable amount of accessory phase occluded therewith, andx, y, a, and z have values within the following ranges:

16 Claims, N0 Drawings This invention relates to synthetic magnesianaluminosilicates, and more particularly to saponite-like compositionsincluding accessory magnesium oxide and/or hydroxide, and still moreparticularly to highly swelling products obtained in accordance with theinvention.

Among clays generally,-a special group of clay types exists, which arecharacterized by swelling behavior in water. This group is in contrastto the clays used for thousands of years for ceramic purposes, in whichswelling is a disadvantage since it leads to excessive shrinkage in theproduction of ceramic articles. This swelling group is characterized bya flat crystal habit in which the equilibrium distance between theindividual flat crystallites is dependent upon the water content as wellas other influences such as the electrolyte content of the water incontact with the clay. The term smectite has been revived in recentyears to embrace the so-called montmorillonite group of clays whichincludes such well known members as montmorillonite, beidellite,nontronite, saponite, hectorite, andsauconite. A discussion and furtherdetails on smectites may be found in the book Rock Forming Minerals,Volume 3, Sheet Silicates, by W. A. Deer et al., London 1962, pages226-245.

Of the smectites, montmorillonite has been widely employed since aboutthe turn of the century in the form of naturally occurring bentonite,for those properties which it possesses as a result of its ability toswell and gel in water. Another member ofthe group, hectorite, has beenemployed as widely as its relative rare occurrence permits, for many ofthe same uses as for montmorillonite, in which it generally ispreferable because of its greater swelling behavior and white color.Because the smectites have inherently negatively charged crystallattices and therefore have chargebalancing cations in positions subjectto exchange by other cations, an entire technology has arisen in thelast 25 years or so in which organic cations are employed exchanged uponsmectites, particularly montmorillonite and hectorite, to obtainproducts which are swellable in organic solvents, the so-calledorganophilic bentonites and organophilic hectorites.

With the high and varied utility of the smectites, it is not surprisingthat some of them have been successfully synthesized on a commercialscale, particularly hectorite. For some uses the considerably highercost of the synthetic products as compared with the natural is not a barto their economic useage.

One disadvantage possessed by smectites generally is that their abilityto swell in water is sharply reduced by the presence of electrolytesdissolved therein. Typical results showing the effect of variouselectrolytes such as sodium chloride, magnesium sulfate, and others, maybe found in the classical paper, The Swelling of Bentonite and ItsControl by C. W. Davis, Industrial and Engineering Chemistry 19,l,3501,352 (l927).

An object of the present invention is to provide a novel product and aprocess for producing the said product, which is a smectite compositionakin to saponite containing intimately admixed and occluded hydrousmagnesium oxide, the said products having extraordinary swellingbehavior in water and in aqueous electrolyte solutions, and having wideutility generally.

Other objects of the invention will appear as the description thereofproceeds.

Generally speaking, and in accordance with illustrative embodiments ofthe invention, I provide a saponite-like mineral composition having'thefollowing formula per unit cell:

and ifi which the co flentsof the braces constitutes the unit cell ofthe saponite-like mineral and y Mg (0,0I-l) is the variable amount ofaccessory phase occluded therewith and whichas the formula indicates ismagnesium oxide or magnesium hydroxide or any of the hydrous magnesiumoxide species and mixtures thereof intermediate between these two endmembers. The compositional variables, x, y, and a, may assume any valuewithin the following limits:

0.1 s x s 1.5

0 a 2 with the preferred values being close to x equals.0.5, y equals 1,and a equals zero. M is the charge-balancing cation, as explainedhereinbelow, having a valence of z, and is most conveniently andpreferably sodium ion, but may also be any other alkali metal oralkaline earth metal cation or ammonium ion or substituted ammonium ion,such as tetraethyl ammonium; ormixtures thereof. It will be clear thatif a mixture is present in which the ions M have different valences,then z will be an average value for the mixture. Further, the contentsof the square brackets represents the fixed lattice portion of the unitcell, which as will be seen from totalling up the positive and negativecharges of the ions contained in this lattice and shown in the squarebrackets, is negative. The charge-balancing positive charges are shown,outside of the square brackets but within the braces, and as will beseen from the above formulation, these charge-balancing cations arerepresented by M. Furthermore, the hydrous magnesium oxide accessoryphase, as will be explained in more detail hereinbelow, is not merelyadmixed with a previously formed saponite-like phase, but is present inthe synthesis reaction mixture so that itis present at the time thecrystal lattice within the square brackets is formed, and is thusintimately associated therewith, for which the term occluded therewithis fitting.

In order to prepare the novel products in accordance with the invention,an aqueous reaction mixture in the form of an aqueous slurry is preparedcontaining mixed hydrous oxides of silicon, aluminum, and magnesium, andsodium (or alternate cation or mixture thereof) hydroxide with orwithout, as the case may be, sodium (or alternate cation or mixturethereof) fluoride in the proportions defined by the above formula andthe preselected valuesof x, y, and a for the particular product desired.Optionally, but preferably, the slurry is allowed to agefor at least 8hours at room temperature after having been formed. The slurry is thenplaced in an autoclave and heated under autogenous pressure to atemperature within the range of approximately to 325C. and preferablyabout 300C. for a sufficient period of time for the inventive product toform by the hydrothermal synthesis thus brought about. Formation timesof 3 I05 hours are typical, and the optimum time for a given preparationcan readily be determined by toclave and contents are permitted to coolto room temperature and the contents removed. In general, no washing ofthe product is necessary, but the entire contents may simply be spraydried or otherwise dried and ground if desired.

When a is selected to be zero, so that fluorides are not present, aconvenient way to add the required amounts of alumina and sodiumhydroxide is in the form of sodium aluminate, NaA1O This results in thenumber of aluminum ions added to the system being accompanied by thesame number of sodium ions, which I find preferable. However,satisfactory products are likewise obtained when the number of aluminumions exceeds the number of sodium ions'or equivalent selected cation ormixture of cations, such as potassium, lithium, calcium, ammonium, andthe like.

Some specific examples will now be given, together with a tabulation ofsome of the properties of the products obtained.

EXAMPLE I To A pounds of SiO-,., as a polysilicicacid sol prepared fromNa-silicate solution by the teachings of U.S. Pat. No. 3,649,556, wereadded a solution of B pounds of sodium aluminate (Na O. A1 3 H O)dissolved in a minimum amount of water, and C pounds of calcinedmagnesite (assaying 92.7% MgO) as a slurry prepared by shearing the MgOwith water on a Cowles Dissolver. The amount of water was adjusted togive 7% solids and this feed slurry was aged in the feed mix tank, withstirring, for hours. After such aging, the slurry was diluted to 4%solids and then pumped to a l40-gallon autoclave. Hydrothermal treatmentwas at 300C. and 1,240 psig for 4 hours; the time for the autoclave tobe heated from room temperature to 300C. was 12 /2 hours. The productslurry was discharged from the autoclave through a quench condenser andthen spraydried.

For several runs, the values of A, B, and C, and of the parameters x, y,and a are given in Table- 1.

Table 1 Sample A B C x y a Some rheological properties of 2.5% (drybasis) dispersions in waterand in salt solution of the productsdescribed in Table l are listed in Table 2. The viscometer used was aFann V-G meter (See Savins, U.S. Pat. No. 2,703,006 for design andtheory).

Note that when y equals zero, unsatisfactory rheological properties areobtained, and indeed, this preparation (Sample ll) is outside the scopeof the invention.

EXAMPLE II Plant-scale synthesis was accomplished from a polysilicicacid sol as described in- Example I, hammermilled calcined magnesite,alumina trihydrate, and liquid caustic (50% NaOH). The magnesite wassheared in tap water by means of a Cowles Dissolver, and the resultingslurry added with agitation to the polysilicic acid sol. The properamounts of alumina trihydrate and caustic were then added, again withagitation. The feed slurry thus prepared was aged about 48 hours (over aweekend), then diluted with water to 4% solids. The feed compositionthus obtained can be described by the following molar ratios:

SiO /MgO 1.088; SiO /Al O 19.7; SiO /NaOH 15.0; the pH was 10.25. Itwill be noted from these ratios that the-composition contained someexcess alumina.

The feed waspumped into an autoclave through a preheater, and attainedin this way a temperature of 150C. at entry to the autoclave. In theautoclave the temperature was increased to 300C. and the pressurecorrespondingly increased to 1,240 psig. The autoclave was maintained atthese latter conditions for 3 to 4 hours and then discharged through aquench condenser. The product slurry was spray-dried.

The product so obtained had the properties listed in Table 3.

Table 3 A. General Properties Moisture, 105C. 8.99 Ignition Loss, 900C,(dry basis) 8.97 Bulk density, lb/ft Uncompacted 61 .5

Compacted 68.6 Cation exchange capacity, meq/ 100 gm Nl-LAc method 56Methylene blue method Calculated from composition 65 Oil Absorption,ASTM C.281-3l, lb/ lb 50 pH value (4% solids in water) 10 Table 4.

B. Viscosity Data(Fresh Water),3.3% solids, Fann V-G meter I ShearStress (dial deflection) Table 5 C. Viscosity Data (ElectrolyteSolutions), lnitial Test, Fann VG meter The data in Tables 4 and 5establish the unique gelling properties of this synthetic product. Theplastic viscosity is low but the gel strength and yield point are highfor a variety of suspending fluids. It is apparent from theserheological data that this product is a useful gellant for fluids asvaried as fresh water, sea water, saturated sodium chloride and calciumchloride solutions, and 1N NaOH.

The data on cation exchange capacity in Table3 include the methyleneblue method result, although this is not reliable in this instance. Theagreement between the calculated figure and the ammonium acetatedetermination is satisfactory.

EXAMPLE 111 Another sample of product made as described for Example 11was converted to the ammonium form by repeated leaching with ammoniumacetate solution. It

was washed, and calcined at 700C. for 4 hours. lts ability to crackcumene was determined by saturating helium with cumene at 55C. andthen'passing it over a 0.25 g sample of the calcined material, ground to30/60 mesh. The reactor temperature was 350C, and the flow rate was 1 ccper second. After onehour of continuous flow, a sampling of the outputshowed a conversion rate of 59.3% of the cumene to propylene andbenzene.

The calcined product had a specific surface area of 307 square metersper gram, as determined by the Brunauer-Emmett-Teller method usingnitrogn as the adsorbate.

EXAMPLE 1V 81.2 g of hammermilled calcined magnesite assaying 92.7% MgOwere added to water and sheared in a laboratory mixer (a CowlesDissolver) to obtain good dispersion of the particles. This slurry wasadded with agitation to 120 g of silica in the form of a polysilicicacid sol containing 5.7% SiO To this mixture there were added withstirring 10.5 g of alumina trihydrate (64.9% A1 0 and l 1.5 g ofNaF.which had been dissolved in a minimum of water. The volume at thisstage was 2.2 liters, all of which was charged into-a l-gallon stirredonly accessory phase. The unit cell formula for the product wasapproximately as follows:

{Mg Si A1 O (OI-1);, F 0.5 Na} 1 MgO The solids content of the slurrywhen placed into the autoclave is not critical. Less than about 2%solids is wasteful from the standpoint of heating losses and throughputfor a given piece of equipment, and in addition, synthesis times may besomewhat prolonged. On the other hand, greater than about 10% solidsgenerally results in a slurry which cannot conveniently be handled byordinary equipment. I prefer from about 3% to about 5% solids in theslurry, as illustrated in the examples given.

The inventive products, as already indicated, have wide utility.Particularlyin the case of'those inventive products in which M isunivalent, and more particularly when M is largely sodium or lithium ora mixture thereof, the ability to spontaneously disperse and swell inwater makes them useful for drilling mud additives; as thickeners andthixotropy imparting agents for water base paints; as thickeners andbodying agents for aqueous cosmetic preparations, dentifrices such astoothpaste, and the like. The large surface area developed upondispersion in aqueous liquids makes them highly useful for theclarification of .beer, wine, vinegar, and honey. Their ability to coatpaper with a thin adherent film makes them useful in the paper sizingart generally, and in particular their cation exchange capacity incombination with their surface catalytic properties especially forcertain organic amines renders them especially useful in those copyingpapers wherein pressure releases microencapsulated color-forming agents,as set forth, for example, in British Pat. No. 773,180.

The cation-exchange capacity also makes possible the conversion of theinventive products to organophilic smectites, for which the generalprocedures set forth in Hauser U.S. Pat. No. 2,531,427, the contents ofwhich are incorporated herein by reference, may be employed. Suchorganophilic smectites in turn have wide utility; they may be used inthe formulation of lubricating greases, as set forth in Jordan U.S. Pat.No. 2,531,440; in paints, varnishes and printing inks, as set forth inRatcliffe U.S. Pat. No. 2,622,987 and the like.

autoclave. The autoclave and contents were heated to those skilled inthe art that many variations are possiblewithout departing from thespirit and scope of the invention.

It will be clear from all of the foregoing, and in particular from theexamples, that my synthetic mineral composition may be used with greatadvantage whenever it is desired to increase the consistency of anaqueous system, including compositions generally having an aqueousphase. The increase in consistency may be followed by any of the knownrheological methods, one of the simplest and most direct of which is thedetermination of the gel strength. The consistency-increasing propertiesof my inventive products are especially marked in those in which theexchangeable cation is an alkali metal cation. In general, simpleaddition of the inventive product to the system suffices, followed whendesired or indicated by stirring or like agitation.

Having described the invention, 1 claim:

1. A synthetic mineral composition having the following formula per unitcell: ii gs r s- 20 4a a)] /Z) +yl in'which the contents of the bracesconstitutes said unit cell of a smectite and in which the contents ofthe square brackets represents the fixed lattice portion of the unitcell, said fixed lattice portion having a negative charge; and in whichM represents cations balancing said negative charge, and wherein z isthe valence of said M, and in which said M is selected from the group ofcations consisting of alkali metal cations, alkaline earth metalcations, ammonium ions, and mixtures thereof; and in which y Mg (0,0H)is an accessory phase occluded with said smectite and consisting ofhydrous magnesium oxide selected from the class consisting of magnesiumoxide, magnesium hydroxide, hydrous magnesium oxide species intermediatetherebetween, and mixtures thereof; and in which said x, said y, said z,and said a have values within the following ranges:

0.1 X 1.5 0.1 y 2 s a g 2 2. A mineral composition in accordance withclaim 1 wherein said x is-approximately equal'to 0.5, said y isapproximately equal to l, and said a is 0.

3. A mineral composition in accordance with claim 1 wherein said M is analkali metal cation.

4. A mineral composition in accordance with claim 2 wherein said M is analkali metal cation.

5. A mineral composition in accordance with claim 3 in which said alkalimetal cation is sodium.

6. A mineral composition in accordance with claim 4 in which said alkalimetal cation is sodium.

7. A process of preparing a synthetic smectite, mineral compositionwhich comprises the steps of forming an aqueous slurry containing mixedhydrous oxides of silicon, aluminum, magnesium, and M and fluoride inthe proportions defined in accordance with claim 1 and the preselectedvalues of the variables in said claim 1 by adding said components towater;

heating said slurry under autoclave conditions under autogenoustemperature within the range of approximately lOOC to 325C. for asufficient period of time for the mineral composition defined by claim 1to form; cooling said mixture; and recovering said mineral compositiontherefrom.

8. A process in accordance with claim 7 wherein said x is approximatelyequal to 0.5, said y is approximately equal to l, and said a is equal toO.

9. The process in accordance with claim 7 wherein said M is sodium.

T0. The process in accordance with claim 7 wherein said slurry ismaintained at room temperature for at least 8 hours before said heating.

11. The process in accordance with claim 8 wherein said slurry ismaintained at room temperature for at least 8 hours before said heating.

12. The process in accordance with claim 9 wherein said slurry ismaintained at room temperature for at least 8 hours before said heating.

13. The process of increasing the consistency of an aqueous system whichcomprises the step of adding to said system a quantity of the mineralcomposition of claim 1 sufficient to substantially increase saidconsistency.

14. The process of increasing the consistency of an aqueous system whichcomprises the step of adding to said system a quantity of the mineralcomposition of claim 3 sufficient to substantially increase saidconsistency.

15. A composition of matter consisting essentially of an aqueous phaseand an amount of themineral composition of claim 1 sufficient to imparta gel strength to said composition of matter greater than in the absenceof said mineral composition.

16. A composition of matter consisting essentially of an aqueous phaseand an amount of the mineral composition ofclaim 3 sufficient to imparta gel strength to said composition of matter greater than in the absenceof said mineral composition.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,855,147 DATED December 17, 197A INVENTOR(S) William '1. Granquist Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the abstract; in Column 2, lines 9 and 10; and in Claim 1, lines 3and thereof, correct the forrnula as follows: {[Mg Al Si o (OH F y Mg(0,0H) and c orrect the last four lines of said abstract to read asfollows: C

o 2 a e2 Signed and Scaled this A ttes I.

RUTH C. MASON v C. MARSHALL DANN Commissioner uj'latents and TrademarksA Hosting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3,855,147 DATED December 17, 197 4 INVENTOR(S) William T.Granquist It is certified that error appears in the above-rdentifiedpatent and that said Letters Patent are hereby corrected as shown below:

In the abstract; in Column 2, lines 9 and 10; and in Claim 1, lines 3and t thereof, correct the formula as follows: {[Mg Al Si o (oH F y Mg(0,0H)

and correct the last four lines of said abstract to read as follows:

O 2 a E. 2

Signed and Sealed this Ninth Day of November 1976 [SEAL] Arrest:

RUTH C. M A SON C. MARSHALL DANN UNK f/ifl Commissioner nj'PaIents andTrademarks

1. A SYNTHETIC MINERAL COMPOSITION HAVING THE FFOLLOWING FORMULA PERUNIT CELL: (MG6AIXSI)-X O20 (OH4-AFA))X- (XMZ/Z)+YMG (O,OH) IN WHICH THECONTENTS OF THE BRACES CONSTITUTES SAID UNIT CELL OF A SEMCTITE AND INWHICH THE CONTENTS OF THE SQUARE BRACKETS REPRESENTS THE FIXED LATTICEPORTION OF THE UNIT CELL, SAID FIXED LATTICE PORTION HAVING A NEGATIVECHARGE; AND IN WHICH M REPRESENTS CATIONS BALANCING SAID NEGATIVECHARGE, AND WHEREIN Z IS THE VALENCE OF SAID M, AND IN WHICH I SAID M ISSELECTED FROM THE GROUP OF CATIONS CONSISTING OF ALKALI METAL CATIONS,ALKALINE EARTH METAL CATIONS AMMONIUM IONS, AND MIXTURES THEREOFF; ANDIN WHICH Y MG (O,OH) IS AN ACCESSORY PHASE OCCLUDED WITH SAID SMECTITEAND CONSISTING OF HYDROUS MAGNESIUM OXIDE SELECTED FROM THE CLASSCONSISTING OF MAGNESIUM OXIDE, MAGNESIUM HYDROXIDE. HYDROUS MAGNERSIUMOXIDE SPECIES INTERMEDIATE THEREBETWEEN, AND MIXTURES THREOF; AND INWHICH SAID X SAID Z AND SAID A HAVE VALUES WITHIN THE FOLLOWING RANGES:0.1 $ X $ 1.5 0.1 $ Y $ 2 Q $ A $ 2 1 $ Z $
 2. 2. A mineral compositionin accordance with claim 1 wherein said x is approximately equal to 0.5,said y is approximately equal to 1, and said a is
 0. 3. A mineralcompositioN in accordance with claim 1 wherein said M is an alkali metalcation.
 4. A mineral composition in accordance with claim 2 wherein saidM is an alkali metal cation.
 5. A mineral composition in accordance withclaim 3 in which said alkali metal cation is sodium.
 6. A mineralcomposition in accordance with claim 4 in which said alkali metal cationis sodium.
 7. A process of preparing a synthetic smectite mineralcomposition which comprises the steps of forming an aqueous slurrycontaining mixed hydrous oxides of silicon, aluminum, magnesium, and Mand fluoride in the proportions defined in accordance with claim 1 andthe preselected values of the variables in said claim 1 by adding saidcomponents to water; heating said slurry under autoclave conditionsunder autogenous temperature within the range of approximately 100*C to325*C. for a sufficient period of time for the mineral compositiondefined by claim 1 to form; cooling said mixture; and recovering saidmineral composition therefrom.
 8. A process in accordance with claim 7wherein said x is approximately equal to 0.5, said y is approximatelyequal to 1, and said a is equal to
 0. 9. The process in accordance withclaim 7 wherein said M is sodium.
 10. The process in accordance withclaim 7 wherein said slurry is maintained at room temperature for atleast 8 hours before said heating.
 11. The process in accordance withclaim 8 wherein said slurry is maintained at room temperature for atleast 8 hours before said heating.
 12. The process in accordance withclaim 9 wherein said slurry is maintained at room temperature for atleast 8 hours before said heating.
 13. The process of increasing theconsistency of an aqueous system which comprises the step of adding tosaid system a quantity of the mineral composition of claim 1 sufficientto substantially increase said consistency.
 14. The process ofincreasing the consistency of an aqueous system which comprises the stepof adding to said system a quantity of the mineral composition of claim3 sufficient to substantially increase said consistency.
 15. Acomposition of matter consisting essentially of an aqueous phase and anamount of the mineral composition of claim 1 sufficient to impart a gelstrength to said composition of matter greater than in the absence ofsaid mineral composition.
 16. A composition of matter consistingessentially of an aqueous phase and an amount of the mineral compositionof claim 3 sufficient to impart a gel strength to said composition ofmatter greater than in the absence of said mineral composition.